Methods of manufacturing yarn without applying true twist have many advantages over conventional methods of spinning wherein true twist is applied. Typical examples include those in which fibers are wound around a core bundle by false twisting them with a fluid, those in which fibers are interlaced by the utilization of currents of fluid, and those in which a yarn is formed by bonding fibers with a binder. Such procedures permit high productivity from a high-speed operation, reduce the number of manufacturing procedures and provide ease of operation of equipment. Further advantages include the capability of producing the final yarn package with no rewind and direct delivery of finished yarns in large packages. Such systems realize large savings in energy and have other advantages as well. Vigorous efforts are being made in many quarters for the further development of such methods.
However, the yarn having properties most similar to conventional true twist yarn is the fasciated fiber yarn which has a core comprising a bundle of virtually non-twisted fibers--mainly staple fibers--and which has staple fibers wound around the surface of the bundle of core fibers. In the United States, such yarn has been placed into production on a commercial basis under the trade name "ROTOFIL".
Problems and limitations have heretofore been encountered in manufacturing such fasciated fiber yarn. Difficulties have arisen in transmitting, at the outlet of the draw zone, fibers floating around the bundle of fibers but which are intended to become the wrapper fibers. Problems have also arisen with respect to the properties required of slivers, the requisite of the means for forming the yarn, and so forth.
Also, the strength of true twist yarns, in general, exceeds that of known fasciated yarns, which in turn exceeds the strength of open-end spun yarns. (See the report of Symposium International Recherches Textiles Cotonnieres"--in Paris, April, 1969, pp. 249-265; the "Textile Industry", November, 1972, etc.).
Typical U.S. Patents disclosing methods of making fasciated yarn include those to Field No. 3,079,746, Yamagata et al No. 3,978,648 and Yamagata et al No. 4,003,194, the latter two being assigned to the assignee hereof. The former Yamagata et al patent discloses a means for transmitting the peripheral fibers, utilizing a conveyor apron band which causes the peripheral fibers to wrap the core fibers in an effective and orderly manner. The Field patent discloses an aspirator as a means of transmission.
In known fasciated fiber yarns the non-twisted core bundle of fibers assumes a more or less zigzag form by reason of the twist shrinkage of the wrapper fibers themselves. Even then the strength of the fasciated fiber yarn has been found to be somewhat less than that of ring spun yarns. The wrapper fibers of known fasciated yarns have sometimes tended not to form or to form irregularly, creating yarn portions wherein the wrapper fibers did not have enough strength to fasciate the core bundle of fibers, thus causing yarn breakage by fiber slippage under high tension.
It has been found that formation of such faulty yarn portions may be attributed to several occurrences in the draft zone. One typical example is the presence of fibers floating around the bundle of fibers, that is, the fibers which are intended to become the wrapper fibers are blown off due to some external factor such as turbulent flow of air. As another example, the air jetting holes of the false twist air vortex nozzle becomes clogged in a manner to inhibit their twist-imparting capability. As a still further example, sufficient means are not provided for transmitting and applying the wrapper fibers to the core fibers.
It is an object of this invention to provide a fasciated fiber yarn producing method which overcomes this problem. Still another object is to bring the strength of the fasciated fiber yarn up to the level of ring spun yarn.
In conventional processes, drawing was carried out by the wet process, using steam or hot water. While this permitted relatively uniform drawing, it required large-scale drying equipment in order to reduce tow water content after drawing below 1 to 2 percent, requiring high equipment cost and consuming considerable energy for drying. From the economic viewpoint, it was necessary to make the tow as heavy as several hundred thousand to several million denier. However, it is then necessary to conduct many tow processing steps to obtain roves of proper thickness for making yarns, so that even though once uniform tows are products, the uniformity of it is disturbed and neps or slubs appear, leading to the lowering of uniformity of tows; and, besides, the complexity of these added process steps makes the yarns produced very expensive. The alternatives was to use undrawn tow of lower denier but then the productivity was extremely low and the manufacturing cost was very high.
There have heretofore been many attempts using both wet and dry processes to eliminate such drawbacks, wherein undrawn uniform tow is drawn and is then continuously subjected to one draft cutting operation and then to another draft cutting operation, in an attempt to obtain uniform sliver.
In wet process drawing of this type it was difficult to dry the tow well enough and this created draft cut irregularities; hence, it was difficult to obtain uniform silver or to obtain high strength fasciated fiber yarn.
In the dry process using hot plates, it is impossible to carry out uniform drawing of undrawn tow heavier than tens of thousands of denier and, hence, to carry out uniform draft cutting. Therefore, draft cut irregularities occur and single yarns break off and wind over the roller.
It has now been discovered that, even with the dry process, it is possible to obtain uniform tow of high quality by special dry heat drafting. By draft cutting using this tow, it is possible to obtain uniform sliver of high strength, quality and uniformity.
It is a still further object of this invention to overcome the drawbacks which have hitherto been found with fasciated fiber yarn and to provide a novel and very special type of fasiciated fiber yarn which has the advantageous properties of true-twist yarn or even better.